1. Field of the Invention
The present invention relates to a conductive printed board and an ultrasonic probe using this conductive printed board, and more particularly to an ultrasonic probe wherein productivity is improved by enabling the use of the conductive printed board as a common part.
2. Description of the Related Art
An ultrasonic probe is used in, for example, ultrasonic diagnostic equipment for medical use, as a transducer which transmits and receives ultrasonic waves. One example of such an ultrasonic probe is an array type ultrasonic probe, in which a plurality of piezoelectric elements having electrodes on both the faces are arranged in a line, and generally the electrodes are led out by a conductive printed board. From recently there are various types of ultrasonic probes distinguished by the number of piezoelectric elements and their array pitch, leading to a call for communization (use as a common part) of the conductive printed board.
FIG. 7A and FIG. 7B show a conventional example of an ultrasonic probe, wherein FIG. 7A is a partially cutaway front view and FIG. 7B is a side view.
As shown in FIG. 7A and FIG. 7B, in conventional ultrasonic probes, a plurality of piezoelectric elements 42 which have excitation electrodes 41a and 41b on both major faces are arranged in a line with defined array spacing (pitch interval d) upon a backing material 43, and connected to an excitation electrode 41a provided on the bottom surface of the piezoelectric elements 42 by conductive wires 45 of a flexible printed board 44. Furthermore, the excitation electrodes 41b on the top surfaces of the piezoelectric elements 42 are connected commonly by a conductor, for example, and are thereby connected electrically to other conductive wires 45 of the flexible printed board 44. In addition, in the case of medical use, an acoustic matching layer not shown in the diagram (to achieve acoustic matching with a living organism), and if needed an acoustic lens (for changing emitted ultrasonic waves into a narrow beam), are provided on the piezoelectric elements 42.
Normally, as shown in FIG. 7B, a piezoelectric plate comprising the excitation electrodes 41a and 41b and the piezoelectric element 42, is connected to the flexible printed board 44, for example, and fixedly secured to the backing material 43. As shown in FIG. 8A and FIG. 8B, the flexible printed board 44 has a plurality of fine conduction paths 45 arranged in parallel or other directions. The conduction paths 45 shown in FIG. 8A and FIG. 8B connect to contiguous terminals 46 provided at the tips of the conduction paths, which are later divided (see FIG. 8A). Alternatively, the conduction paths 45 are connected to terminals 46 which are arranged with the same array spacing d as the piezoelectric elements 42 (see FIG. 8B). Cuttings 47 are then made in the piezoelectric elements 42 from the top of the acoustic matching layer to the backing material 43 thereby severing the piezoelectric elements 42 and dividing the piezoelectric elements 42 into individual piezoelectric elements 42 and terminals 46 arranged at the defined array spacing d (see FIG. 7A).
However, in some cases, with such conventional ultrasonic probes, as shown in FIG. 9A and FIG. 9B, a different array spacing d may be used (using d2instead of d1) for the same number of piezoelectric elements 42. Therefore, it is necessary to separately design a different flexible printed board for use with each of the different array spacings (d1, d2). Consequently, the flexible printed board 44 cannot be used as a common part, which presents a particular problem in that the more types of ultrasonic probes there are, the more inventory is required, which lowers productivity.
The present invention also relates to a multicore cable and an ultrasonic probe using the multicore cable, and relates particularly to a multicore cable which maintains flexibility.
As mentioned above, an ultrasonic probe is a transducer which transmits and receives ultrasonic waves, used for example in ultrasonic diagnostic equipment for medical use. Normally, an ultrasonic probe comprises a probe main body including a plurality of piezoelectric element groups arranged in a line, and a multicore cable which connects the probe main body electrically to the main body of the diagnostic tool (see Japanese Laid-Open Patent Publication No. 2003-102732, for example). Recently, for medical and operational reasons, there is a call for smaller and lighter ultrasonic probes.
FIG. 10 and FIG. 11A to FIG. 11C show a conventional example of such an ultrasonic probe, wherein FIG. 10 is a sectional view of the ultrasonic probe, FIG. 11A is a front view of the probe main body, FIG. 11B is a side view thereof, and FIG. 11C is a partially cut away back view thereof.
Normally, as shown in FIG. 10, the ultrasonic probe comprises a probe main body 61 and a multicore cable 62, and the probe main body 61 is housed within a case 63. Also, a construction is used in which piezoelectric element groups 65 arranged in a line upon a backing material 64 are exposed through an opening in the case 63. Normally, an acoustic matching layer and an acoustic lens (neither shown in the drawing) are provided on the piezoelectric element groups 65, and the piezoelectric element groups 65, on the major faces of which are provided excitation electrodes 65a and 65b, are connected to the back surface of the backing material 64 by means of a flexible printed board 66, for example.
Furthermore, as shown in FIG. 11A to FIG. 11C, the flexible printed board 66 comprises a resin film 66a in which a plurality of signal conductors 67 are provided. The excitation electrodes 65a and 65b of the piezoelectric element groups 65 are bonded to the signal conductors 67 by solder or the like as shown in FIG. 11A, to establish an electrical connection. Moreover, the excitation electrodes 65b on the bottom surface side (the backing material 64 side) of the piezoelectric element groups 65, and the signal conductors 67 of the flexible printed board 66 are connected. Also, the top surface side (transducer side) of the piezoelectric element groups 65 is connected commonly by conductors (not shown), for example, to form a grounding surface, which is connected to a grounding wire of the flexible printed board 66.
In addition, as shown in FIG. 12A, a multicore cable 72 comprises a plurality of coaxial cables 73 (for example 128 cables) sheathed within an outer jacket 70. The coaxial cables 73, as shown in FIG. 12B, have a four-layered construction comprising a central conductor 73a, a first insulating material 73b, a braided shield 73c and a second insulating material 73d, layered concentrically. The central conductor 73a of each coaxial cable 73 is connected to a signal conductor 67 on the flexible printed board 66, and the braided shield 73c is connected to another signal conductor 67 for grounding the flexible printed board 66. In addition, the outer jacket 70 is made of a resin or the like, which demonstrates flexibility. Normally, a shielding material 71 is provided on the inner surface of the outer jacket 70, collectively shielding the plurality of coaxial cables 73.
However, because the conventional ultrasonic probes as described above use four-layered coaxial cables, it is not possible to reduce the diameter of the multicore cable 72. Furthermore, the terminals 68 of the signal conductors provided on the flexible printed board 66 (see FIG. 11C) cannot normally be provided at narrower spacing than the diameter of the coaxial cables 73, which impedes miniaturization. Accordingly, there is a problem in that the greater the number of piezoelectric elements, that is the greater the number of channels, the larger the diameter of the multicore cable 72, which prevents miniaturization.
Specifically, when an ultrasonic probe for medical use is to be inserted into a body cavity, the multicore cable 72 cannot have a large diameter. Consequently, increasing the number of channels, for example in order to improve resolution of the ultrasonic probe, is problematic. In addition, there is a problem in that it is difficult to integrate a medical catheter with an ultrasonic probe, for example, preventing multifunctionality from being achieved. Furthermore, because an ultrasonic probe according to the conventional example is constructed with bundled coaxial cables, there is a problem in that such an ultrasonic probe is heavy, and therefore operability is poor.